We use the model DIETER, introduced in a companion paper, to analyze the role of power storage in systems with high shares of variable renewable energy sources. The model captures multiple system values of power storage related to arbitrage, capacity, and reserve provision. We apply the model to a greenfield setting that is loosely calibrated to the German power system, but may be considered as a more generic case of a thermal power system with increasing shares of variable renewables. In a baseline scenario, we find that power storage requirements remain moderate up to a renewable share of around 80%, as other options on both the supply and demand side may also offer flexibility at low cost. Yet storage plays an important role in the provision of reserves. If the renewable share further increases to 100%, the need for power storage grows substantially. As long-run parameter assumptions are highly uncertain, we carry out a range of sensitivity analyses. As a general finding, storage requirements strongly depend on the costs and availabilities of other flexibility options, particularly regarding flexible power generation from biomass. We conclude that power storage becomes an increasingly important element of a transition toward a fully renewable-based power system, and gains further relevance if other potential sources of flexibility are limited.
Keywords: Power storage, Flexibility options, Renewable energy, Energy transition, Dispatch and investment model, Open-source model